Lithographic plate and process of making the same



Ffilb. 16, 1943. w T HAGELlN 2,311,047

LITHOGRAPHIC PLATE AND PROCESS OF MAKING THE SAME Filed Dec. 6, 1940 zzg f LITHOGRAC PLATE PROCESS OF G E SAME W T. Hagelin, Chicago, Ill.

Application December 6, 1940, Serial No. 368,753

15 Claims. (Cl. 41-415) This invention relates to a lithographic platemethod of producing the same upon which a and a process of making thesame. More parvery ink-receptive image may be impressed ticularly, thisinvention relates to a process of either by means of direct contact orby means producing a lithographic plate having a surface ofphotolithographic processes. that is very receptive to greasy films suchas may A further object of this invention is the probe applied theretoby crayon, lead pencil, grease vision of a metal surface coating whichis subink, and the like or by a suitable stylus through a stantiallynon-oxidizable even though exposed to tracing sheet such as carbon paperor a typethe atmosphere under conditions normally prowriter ribbon.moting oxidation.

A plate, to be useful in ordinary lithographic A still further object ofthis invention is the work, should be one that is treated in such aprovision of a new etch solution which may be manner that the surfacethereof is adapted readused for the treatment of lithographic plates.ily to receive a grease coating or film such as may Further additionalobjects will appear from be made through a typewriter ribbon or bypenthe following description, the accompanying cil, crayon, or otherdrawing or tracing instrul5 drawing, and the appended claims. ment thatis capable of depositing a greasy film In accordance with one embodimentof this on said surface when contacted therewith. The invention, alithographic plate may be prepared character of the surface should besuch that after from a metal sheet by subjecting one surface of desiredmarkings have been produced thereon, the sheet to a graining treatment,and then subthe portions of the surface not coated with the jecting saidsurface to the action of an alkali markings or grease film may besubjected to a earth metal oxide and silica in the presence of treatmentwhereby those portions of the surface water. These compounds apparentlyreact with will be rendered ink-repellent while the coated the metallicsurface of the lithographic plate to portions remain very receptive togreasy subform a deposit or coating which is extremely restances such aslithographic ink. Consequently, ceptive to markings which may beimpressed when the lithographic plate having an image imthereon by agrease-containing stylus such as pressed thereon is passed under aroller containa crayon or lead pencil, or which may be iming a greaseink, the ink will adhere only to that pressed thereon through ordinarycarbon paper portion of the plate to which the grease film or or atypewriter ribbon. The deposit renders the markings have b pp and areproduction surface of the metal treated very resistant to 01' t emarkings y be transferred directly to oxidation and the treated platesmay be stored the surface to be printed or to a cylinder having for longperiods of time,

a rubber blanket which in turn transfers it to the The process ofproducing lithographic plates desired surface in accordance with thecommon of this invention may be continuous. In accordpmtlce. It istherefore important in the lithoance with one embodiment of thisinvention, a graphic art that lithographic plates have a surcontinuousthin metal strip is passed under a face which at one time is stronglyreceptive to revolving wire brush in order to remove foreign markingswhich may be produced by greasy mamaterial from one surface of thestrip, and to t r als. ut w h surf s a so of s h a charimpart a desiredgrain thereto. The resulting deter that it y be treated to render it easstrip is then subjected to a scrubbing or brushrepellent except in thoseportions of the surface ing action in the presence of substantial quantowhich the greasy film or markings have been titles of a mixture of lime,finely divided silica, applied. and water. During this scrubbing actiona de- It is an object of this invention to provide an posit or coatingforms on the surface of the i pr ved ith raph p at which is ap ble ofmetal sheet which is subsequently brushed and readily receiving a greasyfilm from any sort of washed with water and thoroughly dried. The adrawing instrument, stylus or stencil capable deposit or coatingsurvives the subsequent washof depositing on said surface agrease-containing ing and drying operations and is of such a nature filmin selected areas. that the surface of the resulting metal is very Afurther object of this invention is to provide receptive to greasemarkings imparted by cona continuous process of preparing a lithographictact or to other images produced in accordance plate having the aboveindicated desirable charwith well known photolithographic processes.acteristics. The thus treated metal sheet may then be A further objectof this invention is the promarked, scored, cut and packaged as desired.

vision of a flexible lithographi Plate and a It will, or course, berecognized that any type lithographic art. If desired, a. thin metalsheet may be employed which has a. paper backing adhesively securedthereto. Thi paper backing is preferably waterproofed and secured to thesheet metal with a waterproof adhesive, so that subsequent contact ofthe resulting plate with water during treatment and during use will notcause separation of the paper and metal sheet. Also, while it ispreferred to employ a mixture of water, lime and finely divided silicaas the treating agent for the plate to form the desired grease-receptivedeposit, it has been found that other alkali earth metal oxides may bsubstituted for the lime. Suitable substitutes are the oxides of barium,magnesium, and strontium. Under certain conditions, varioussilica-containing abrasives may be substituted for the silica, or otherfinely divided abrasives may be used. such as pumice, finely dividedargillaceous materials and the like. I However, I prefer to use finelydivided silica of a fineness sufilcient to pass a 250 mesh screen. It isthe combination of the alkali earth metal oxide with silica and waterwhich appears to produce the desired coating or deposit. Under certainconditions, a water-soluble blue dye may be incorporated with thetreating mixture in order to impart a desirable whiteness to the coatingon the resulting plate. Only traces of the blue dye may be used, asuitable one being a water-soluble dye known as benzoyl blue.

For a more complete understanding of this invention, reference will nowbe had to the drawing, wherein Figure 1 is a diagrammatic elevationalview of an apparatus which may be used for a continuous process ofproducing a lithographic plate in accordance with one embodiment of thisinvention.

Fig. 2 is a greatly enlarged partial sectional view of a lithographicplate prepared in accordance with one embodiment of this invention,having the coating or deposit of ink-receptive material thereon.

Fig. 3 is similar to Fig. 2. but shows a product having a backing ofwaterproofed paper adhesively secured to the sheet.

Referring now more particularly to Fig. l, a roll ill of thin sheetmetal is provided which is capable of being unrolled to advance acontinuous strip of metal l2 over a table M of Monel metal, glass, orother corrosion-resistant material, by means of drawing rolls I 6. Thesheet l2 may be a thin metal sheet of aluminum or zinc or otherlithographic metal having a thickness of about liooo inch. Such a sheetis flexible and is, when treated, capable of being inserted into thecarriage of an ordinary typewriter and positioned on the drum of anordinary lithographic machine. If desired, the metal sheet l2 may beprovided with a paper backing It, as indicated in Fig. 3. In such case,the metal sheet may have a thickness of about @5000 inch, and thebacking a thickness of about $5000 inch. The backing is preferablywaterproof paper, and adhered to the metal sheet l2 by means of awaterproof adhesive. It will be understood. of course, that the metalsheet or the metal sheet and paper backing may be of any desiredthickness and I do not wish to limit myself to the particular asiaoavdimensions indicated above. The metal surface of the strip l2 has been,prior to the time that it is rolled into the roll 10, treated with awire brush, in order to remove foreign matter from the surface of themetal and to provide a. suitable roughness or grain to the surfac of thestrip to be treated.

The strip I 2 having the grained surface is pulled continuously from theroll I0 by means of the drawing rollers it under a spout 20 of areceptacle 22 having contained therein a mixture 24!, which is depositedon said strip. The mixture 26 preferably comprises about two parts byweight of calcium oxide, about two parts by weight of finely dividedsilica, and about eight parts by weight of water. A small amount ofbenzoyl blue may also be added thereto in order to provide a desiredwhiteness to the coated surface of the resulting product. The mixture 2%within the receptacle 22 is continuously stirred by a paddle 26 operatedby means (not shown) through a belt 28. By this means, the ingredientsin the mixture 24 are kept in uniform suspension and undesirablesettling is prevented.

The mixture 24 is deposited through the spout 20 onto the grainedsurface of the metal sheet it which is continuously advanced under adoctor blade 30 serving evenly to distribut the mixture over the entiresurface of the sheet. The thus covered sheet is then passed over thetable It and under a plurality of oppositely rotating brushes 32 whichserve to scrub the surfaces of the sheet in the presence of the mixtureof lime, silica, and water, and to thoroughly contact the mixture withthe grained surface of the sheet. The sheet I2 is then advanced under asqueegee it in order to remove excess quantities of the mixture, andthen is advanced under a plurality of washing brushes 36 which alsorotate in opposite directions and serve to remove all traces of excessquantities of silica and lime from the surface of the sheet. Water forthe washing plurality of pipes 38 positioned thereabove. The

corrosion-resistant table Iii serves as a backing for the scrubbingbrushes 32 and the washing brushes 36.

The strip l2, after having been washed, is then passed under acloth-covered wiping roll 39 and between the drawing rolls l6, whichlatter serve to pull the sheet l2 across the table It, and which alsoserve to squeeze excess quantities of water from the sheet l2, in casesuch sheet has a paper backing, as indicated in Fig. 3. The sheet I2 isthen advanced through a drying chamber to, which is equipped with aplurality of drying lights 42 positioned above and below the sheets. Theproduct here may be re-rolled if desired and may be subsequently marked,out and packaged as needed. However, as shown in the drawing, it is feddirectly from the drying chamber 40 into a printing mechanism M, whichprints, with water color ink, markings to serve as guide marks on theresulting product, and thereafter it is fed into a scoring device 46,and to the cutters it, which serve to cut the sheet to the desiredlengths. The separate sheets may then be stacked and packaged in anydesired manner.

It will, of course, be recognized that both surfaces of the strip I2 maybe treated in accordance with this invention. It is, in such a case,necessary to subject both sides to a prior wire brushingbr grainingoperation before treating the product as herein disclosed. This doubletreatment may be applied to both sides of a metal sheet or to theexposed surfaces of two metal sheets adhered to each side of awaterproofed paper backing by a waterproof adhesive.

It has been discovered that a lithographic plate prepared in accordancewith the process indicated above has many desirable properties whichmake it superior to lithographic plates which have heretofore been usedin the art. It is very receptive to grease, and is consequently veryuseful for accurately reproducing grease markings which may be impressedthereupon. After desired markings have been impressed on the plate,either mechanically by a typewriter or other drawing instrument or by aphotolithographic operation, the surfare of the plate may be wiped witha sponge containing a solution which is known in the lithographic art asan etch solution whereby those portions of the surface not containingthe greasy material or photographic image are rendered ink-repellent. Aparticularly useful etch solution prepared in accordance with thisinvention has the following composition solution to about pH 3.8

This etch has properties which make it, superior to other etches ofwhich I am aware.

After the plate has been treated with the etch solution, it may bemounted on the drum of a lithograph machine and a grease ink may beapplied to the surface of the plate by means of a roll. The ink willadhere only to those portions to which the grease film or markings havebeen applied and the grease ink on these markings may then betransferred directly to the surface to be printed or to a cylinderhaving a rubber blanket which in turn transfers it to the surface to beprinted. A fountain etch may be applied to the plate by means of a waterroll on the lithograph machine in order to insure that the ink-repellentportions of the plate will retain their ink-repelling properties. Inaccordance with one embodiment of this invention, a suitable fountainetch is one which may be prepared by adding an equal quantity ofglycerine (Y. D.) to the etch composition given above,

Plates prepared in accordance with this invention retain their accuracyof reproduction over long periods of time and may be used indefinitely.They are also very resistant to oxidation and the plates may be storedfor long periods of time and re-used. This non-oxidizing coatingimparted to the surface of the metal in accordance with this inventionmay be applied to other metal articles such as they be employed instructural work but, of course, it finds particular use in thepreparation of lithographic plates as herein described.

An important feature of the present invention is the provision of alithographic plate which has been treated with a mixture of water, analkali earth metal oxide and silica. Any desired proportions may be usedbut I have discovered that best results are obtainable when about equalparts of the oxide and silica are used in admixture with a somewhatgreater amount of water. This mixture when applied as indicated aboveforms a deposit or coating on the surface of the lithographic plate.This coating is indicated at 50 in Figs. 2 and 3. I do not understandwhat the true nature of this coating is, nor do I understand the natureof any physical or chemical reactions that may be involved in itsformation. However, I do know that the use of the mixture indicatedresults in an improved lithographic plate which is much more receptiveto grease images than are plates which have been prepared and cleanedwith ordinary abrasives or chemical cleaning agents.

The plate of this invention is extremely finegrained and is capable oftransferring an extremely accurate image. Markings of lead pencil,crayon and grease ink on the plate are accurately reproducible and arereadily distinguishable one from the others on the surface printed withthe plate of this invention. The markings on the plate can be erased incase corrections are desired while the markings are being appliedthereto. Erasures may be made by a stiff glass fiber brush or by meansof a suitable solvent, such as a mixture of equal parts oftrichlorethylene and acetic acid. The erasures are indistinguishable inthe reproduction and fresh markings may be applied to the plate over theerasures.

While particular embodiments of this invention are shown above, it willbe understood, of course, that the invention is not to be limitedthereto, since many modifications may be made, and it is contemplated,therefore, by the appended claims, to cover any such modifications asfall within the true spirit and scope of this invention.

I claim:

1. A process of preparing a lithographic plate which comprises impartinga grain to one surface of a metal sheet, treating said surface with amixture of an alkali earth metal oxide, silica and water, washing saidmixture therefrom, and drying the resulting product, whereby saidsurface has been rendered strongly receptive to impressed greasymarkings.

2. A process of preparing a lithographic plate which comprises impartinga grain to one surface of said plate, Scrubbing said surface in thepresence of a mixture of lime, finely divided silica and water, washingsaid mixture from said surface, and drying the plate, whereby saidsurface has been rendered strongly receptive to impressed greasymarkings.

3. A process of treating the surface of a metal plate to render itstrongly receptive to impressed greasy markings comprising imparting agrain to said surface, brushing said surface in the presence of amixture of lime, finely divided silica and water, then washing saidmixture from said plate, and drying the same.

4. A process of treating the surface of a metal plate to render itstrongly receptive to impressed greasy markings comprising the steps ofwirebrushing said surface to impart a grain thereto, depositing amixture of lime, silica and water on said surface, brushing said surfacein the presence of said mixture with a plurality of oppositely rotatingbrushes, washing and brushing salidt mixture from said surface, anddrying the p a e.

5. A process of treating the surface of a metal strip to render itstrongly receptive to impressed greasy markings comprising imparting agrain to said surface, continuously advancing said strip, depositing amixture of lime, silica and water on said surface, brushing said surfacein the presence of said mixture as the strip continuously is advanced,then washing said mixture from said surface, drying the same, andcutting the strip into predetermined lengths.

6. The process of claim 5 in which said strip is continuously marked andscored prior to cutting. '7. An etch solution for treating the surfacesof lithographic plates comprising water, glycerine, mono-ammoniumphosphate, ammonium sulfate and phosphoric acid.

8. A process of preparing a lithographic plate which comprises treatingthe surface of said'plate with a mixture of an alkaline earth metaloxide, finely divided silica and water whereby a grease receptivecoating is formed thereon, applying desired grease markings to saidsurface, and treating said surface with an etch to rendergreaserepellent those portions of the surface not covered with themarkings, said etch comprising an aqueous solution of glycerine,mono-ammonium phosphate, ammonium sulfate, and phosphoric acid, wherebyto form a fine-grained plate capab'e of transferring an extremelyaccurate image of said grease markings.

9. A process of preparing a lithographic plate which comprises impartinga grain to one surface of a metal sheet, treating said surface with amixture of an alkali earth metal oxide, a finely divided abrasive andwater, washing said mixture therefrom, and drying the resulting product,whereby said surface has been rendered strongly receptive to impressedgreasy markings.

10. A lithographic plate comprising a thin flexible metal sheet havingthe normal lithographic surface thereof grained and treated with amixture of an alkaline earth metal oxide, a finely divided abrasive, andwater to provide a greasereceptive coating thereon.

11. The lithographic plate recited in claim 10 wherein said abrasivecomprises silica.

12. The lithographic plate recited in claim 10 wherein said alkalineearth metal oxide comprises lime.

13. The lithographic plate recited in claim 10 wherein said sheetcomprises aluminum.

14. The lithographic plate recited in claim 10 wherein a sheet ofwaterproofed paper backing is adhesively secured to the opposite surfaceof said metal sheet.

15. A lithographic plate comprising a thin flexible aluminum sheethaving the normal lithographic surface thereof grained and abraded witha mixture of lime, finely divided silica, and water to provide agrease-receptive coating thereon.

WILLIAM T. HAGELIN.

